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Type: Bug
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Resolution: Done
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Priority: Major - P3
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Affects Version/s: 2.8.0-rc0
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Component/s: Performance, Replication, Storage
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Fully Compatible
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ALL
This may be related to SERVER-16235, but filing as a separate ticket since my understanding is that a workaround is in place to prevent SERVER-16235 from impacting the oplog, plus the symptoms here are a bit different, so this may be a separate issue.
Tested on build from master this afternoon (365cca0c47566d192ca847f0b077cedef4b3430e).
- Test on single-node replica set repeatedly updates the document in a single-document collection in order to generate a lot of oplog entries while minimizing work to actually perform each op, in order to emphasize oplog performance.
- Yellow graph below shows declining performance over time (measured in number of updates done). Graph shows same decline starting at first oplog wraparound at about 90 k inserts as seen in
SERVER-16235, but then it recovers and begins a cycle of repeated declines and recoveries. But superimposed on this is a longer term downard trend, and that possibly distinguishes this issue fromSERVER-16235. Not clear from this data whether the asymptote is >0. - Red graph shows that the decline goes away for the same test in a standalone instance, confirming that this is an oplog issue.
- Blue graph shows that decline is not seen with mmapv1, confirming that this is a WT-specific issue.
- Restarting mongod (not shown) resets the behavior back to time 0.
db.c.drop() db.c.insert({_id:0, i:0}) var every = 10000 var bulk = db.c.initializeOrderedBulkOp(); var t = new Date() for (var i=0; i<=count; i++) { if (i>0 && i%every==0) { bulk.execute(); bulk = db.c.initializeOrderedBulkOp(); tt = new Date() print(i, Math.floor(every / (tt-t) * 1000)) t = tt } bulk.find({_id:0}).updateOne({_id:0, i:i}) }
- is depended on by
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SERVER-16366 Gradually degrading performance (wiredtiger)
- Closed
- is related to
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SERVER-16235 Performance issue in capped collections under WiredTiger
- Closed
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SERVER-16379 Chunk moves are slow under WiredTiger
- Closed
- related to
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SERVER-16296 Producer-consumer use case shows declining performance over time under WIredTiger
- Closed